Heater block



FIG. 1 is a top plan view of a heater block in accordance with my design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a longitudinal section view taken along line 4-4 of FIG. 1; and,

FIG. 5 is an enlarged detail view of FIG. 4.

The dashed broken lines depict portions of the heater block that form no part of the claim. The dash dot broken lines depict boundaries of the enlarged detail view and form no part of the claim. 

CLAIM The ornamental design for a heater block, as shown and described. 